Diaphragm type high pressure shut-off valve

ABSTRACT

The invention has its object to provide a diaphragm type high pressure shut-off valve which is simple in external shape, can realize miniaturization and is convenient in handling. 
     The shut-off valve comprises a cylindrical housing (10) having a supply unit for compressed air at its end in an axial direction (Q), a piston (19) provided in the housing (10) and adapted to reciprocate in response to the compressed air, a return spring (20) provided in the housing (10) so as to permit the piston (19) to return, a rack portion (19A) provided to extend from the piston (19), a cam pinion (17) having a pinion portion (17B) provided integrally with the pinion portion (17B) and a rotating shaft (18) supported by the housing (10), and a diaphragm (7) adapted for movement in response to displacements of stems (9,13) and abutting against the cam face portion (17A) of the cam pinion (17). As A drive mechanism and an energizing mechanism are accommodated in the single cylindrical housing, it is possible to realize adequate miniaturization and simplification to thereby contribute to reduction of the number of parts.

FIELD OF THE INVENTION

The present invention relates to a diaphragm type high pressure shut-offvalve provided in a gas piping system for introducing or shutting off ahigh pressure and high purity gas used for production of, for instance,semiconductor devices or the similar purposes.

BACKGROUND TECHNOLOGY

As this type of diaphragm type high pressure shut-off valve, there hasbeen known, for instance, the one described in Japanese Utility ModelLaid-Open Publication No. 131077/1989. In the diaphragm type highpressure shut-off valve described above, a first housing foraccommodating a driving mechanism comprising a piston, a coil spring orthe like and a second housing for accommodating a power amplifyingmechanism comprising a rack pinion, an eccentric disk cam or the likeare provided, a rack for the driving mechanism for supplying compressedair or reducing a pressure thereof is moved in a direction crossing apulsating direction of the diaphragm, a circular and eccentric disk camof the power amplifying mechanism is rotated in association withmovement of the rack described above, and a valve hole is kept in theopen or closed state by a diaphragm contacting an edge portion of a stemcontacting the disk cam in its axial direction.

With the configuration based on the conventional technology describedabove, however, the first and second housings are located side by side,and especially the driving mechanism drives in a direction perpendicularto a direction of pulsation of the diaphragm, so that there are somerestriction in minimization of the housing due to technological limitsin development of material for each mechanism when the presentapplication was filed, and also stress is placed only on the functionsand the external shape is ignored so that the structure has rather anirregular form, and for this reason the conventional type of diaphragmhigh pressure shut-off valve is inconvenient in handling and causes manytroubles in designing of a piping system or installation thereof. Forinstance, when a plurality of shut-off valves are provided side by side,sometimes a length in a direction along which the plurality of shut-offvalves are laid may become too long, of physical interference may occurbetween adjoining shut-off valves, which is disadvantageous.

It should be noted that, in the U.S. Pat. No. 4,700,735, as understoodfrom FIG. 10 and FIG. 11 thereof, a configuration enabling solution ofthe disadvantages caused by providing said first and second housingsside by side is disclosed. In this configuration described above, afirst accommodating portion for accommodating a driving mechanism fordriving a coil spring, a piston or the like and a second accommodatingportion for accommodating a pinion and a power amplifying mechanism foran eccentric cam each attached discretely to the same shaft are providedin a housing, the second accommodating portion is covered with twosheets of detachable plates, the first accommodating portion is piled upon the second accommodating portion for realizing a two-layeredconstruction, a rack provided so that it hangs down over the piston isabutting the pinion, the diaphragm is pulsated by a stem contacting theeccentric cam, thus a valve hole being opened or closed.

In the configuration described above, however, the housing istwo-layered, or it is necessary to use a plate for covering, so thatadequate simplification in at least the general external shape has notbeen achieved.

In addition the coil spring is accommodated in the first accommodatingportion, so that a length thereof is limited to a substantially half ofthe full height, and for this reason, energized force is limitedaccording to the length, which is a severe restriction in minimizationof the configuration.

Furthermore the configuration comprises various components such as apiston, a rack, a pinion, an eccentric cam or the like, so that a numberof parts and a number of processes for assembling the parts are apt tobecome larger.

Furthermore in the two examples of the conventional technology, thepower amplifying mechanism comprises an eccentric cam obtained by makingeccentric a circular disk cam moving in response to driving of thedriving mechanism, and the eccentric cam rotates according todisplacement caused by pulsation of the diaphragm, so that a change in apower amplifying ratio of the power amplifying mechanism due to rotationof the eccentriccam (a ratio of a driving force of the driving portionand a load to the diaphragm) does not coincide with the pulsationcharacteristics of the diaphragm. In other words, the load may be smallwhen an operation of the diaphragm for closing a valve is started, but alarge load is required around a timing when the valve is completelyclosed, which is contradictory to the pulsation characteristics.

Furthermore, as displacement due to pulsation of the diaphragm isdominated by eccentricity of the eccentric cam, so that only a quitenarrow portion of a rotational angle of the eccentric cam contributes todisplacement of the diaphragm, and for this reason not only adjustmentthereof is quite difficult, but also an adjusting mechanism foradjusting a position of a stem against the eccentric cam is required foreach type of product, and it is disadvantageously difficult to keepperformance of products in a fixed range.

It is an object of the present invention to provide a diaphragm typehigh pressure shut-off valve having a simplified external shape, adaptedfor minimization, convenient in handling, operating in response to thepulsation characteristics of the diaphragm, and enabling minimization ofdispersion in terms of quality among products.

DISCLOSURE OF THE INVENTION

To achieve the object as described above, the main configurationaccording to the present invention is characterized in that thediaphragm type high pressure shut-off valve according to the presentinvention having a diaphragm for setting a valve hole for a gas pipingsystem to the open or closed state by increasing or reducing a pressureof compressed air comprises a cylindrical housing having a supply unitfor the compressed air at its edge in the axial direction, a pistonprovided in the housing to reciprocate in response to increase ordecrease of a pressure of the compressed air, a return spring providedin the housing to energize the piston against a pressure of thecompressed air, a rack portion integrally formed with and extending fromthe piston and also having abutting teeth provided along the directionof reciprocal movement of the piston, a pinion abutting the rackportion, a cam surface portion integrally provided with the pinionportion, and a cam pinion supported by the housing and having a rotatingshaft extending in a direction perpendicular to the axial direction, andthat rotational displacement of the cam surface portion of the campinion is delivered through a stem to the diaphragm provided at anotheredge in the axial direction.

FUNCTION

In a case, for instance, an always-closed type, compressed air suppliedto a pressure receiving surface of the piston is reduced, the piston ismoved to the direction of anti-diaphragm by energizing force of thereturn spring, and the rack portion provided integrally with the pistondescribed above is moved to the same direction thereof. With thisconfiguration, abutting rotation in the pinion portion of the cam pinionis started, a stem is moved in the direction of pulsating displacementof the diaphragm along the cam surface portion in accordance withprocessing of the abutting rotation, and the diaphragm corresponding tothe movement makes pulsing displacement in a pressured loaded statethrough the stem. And if the cam pinion is rotated by only a specifiedangle, the valve hole becomes a state of the valve completely closed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a vertical section view of a diaphragm type high pressureshut-off valve according to the embodiments of the present invention;

FIG. 2 is a perspective view of an actuator housing shown in FIG. 1;

FIG. 3 is a plan view of a cam pinion shown in FIG. 1;

FIG. 4 is a side view of a cam pinion taken along the line F--F in FIG.3;

FIG. 5 is a graph illustrating an example of the cam displacement in thecam surface portion of the cam pinion shown in FIG. 1;

FIG. 6 is a graph illustrating a relation between a power increase ratioand a rotating angle of the cam surface portion or an eccentric cam; and

FIG. 7 is a deformed example in a case where a ball 16, a stem 13, andO-ring 14 are removed from FIG. 1.

DESCRIPTION OF THE REFERENCES

4 valve hole, 7 diaphragm, 9 lower stem, 10 housing, 11 actuator housingportion, 12 actuator cover, 13 upper stem, 16 aligning ball, 17 campinion, 17A cam surface portion, 17B pinion portion, 18 rotating shaft,19 piston, 19A rack portion, 20 return spring, Q axial direction, 101a,101b rack piston guide, 100, 106 bushe for rack piston guide, 102needle-shaped roller, 103 needle-shaped roller with external wheels, 104bonnet, 105 stem on which the roller with external wheels can bemounted, 107 stop screw 107.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1

FIG. 1 shows a preferred embodiment of a diaphragm type high pressureshut-off valve of the always-closed type according to the presentinvention, and a valve body 1 connected to a gas piping system forflowing a gas, which is a high pressure (e.g. 245 Kgf/cm²) and highpurity fluid has a cylindrical valve chamber 6 formed around the valvehole 4 erecting from a position close to a valve head of the valve hole4 for a seal 5 with the valve hole 4 communicating to an inlet port 2 aswell as to an outlet port 3 presented therein to be mounted.

The diaphragm 7 is provided covering the valve hole 4 inside the valvechamber 4 and an actuator button holder 8 is provided to hold aperipheral section of the diaphragm with the seal portions 5. A lowerstem 9 having a convex contact surface in a lower section thereofcontacts to a vertex surface portion in a counter valve hole of thediaphragm 7. In addition, a guide hole 8a is formed in a upper sectionof the actuator button holder 8, and an upper section of the lower stem9 penetrates through the guide hole 8a.

On the other hand, provided above the valve chamber 6 is a substantiallycylindrical housing 10, the housing 10 substantially comprises anactuator housing portion 11 in a lower section thereof and an actuatorcover portion 12 screwed to the housing 11 so that it is located abovethe actuator cover 12, and a small diameter portion 11a in a lowersection of the actuator housing portion 11 is screwed to the valvechamber 6. It should be noted that a peripheral portion of the actuatorbutton holder 8 is held between a lower edge of the small diameterportion 11a of the actuator housing 11 and the seal portion 5 describedabove.

Provided above the lower stem 9 is an upper stem 13 with an upper edgeof the lower stem 9 and a lower edge of the upper stem 13 formed into aconvex state and a concave state respectively, and the two edges abuteach other through engagement of the convex and concave portions.

A large diameter head portion 13a is formed in an upper section of theupper stem 13, the large head diameter portion 13a is inserted into anoperation hole 11b formed in the actuator housing portion 11 with anO-ring fitted into a circular groove 13d presented in the large diameterhead portion 13a. Furthermore a coil spring 15 is spanned between aspring receptor 13b of the large diameter head section 13a and a springbase 8b formed in the upper section of the actuator button holder 8.

Also an aligning ball 16 is provided inside the operation hole 11b, thealigning ball 16 is placed on a concave base surface 13c formed at anupper edge of the upper stem 13, and the aligning ball 16 contacts a camsurface portion 17A of a cam pinion 17.

The cam pinion has a disk-like form as a whole with a said cam surfaceportion 17A constituting a power amplifying mechanism and a pinionportion 17B connected thereto formed in a substantially semi-circularform respectively therein, and can freely rotate around a rotating shaft18.

Provided above the cam pinion 17 in the actuator cover portion 12 is apiston 19 constituting a driving mechanism, and in the piston 19 a rackportion 19A abutting the pinion section 17B is integrally provided in ahanging state, and the rack portion 19A reciprocates along alongitudinal direction of the rack guide 11c formed in a portion of aperiphery of the actuator housing portion 11.

Provided between the piston 19 and the actuator housing portion 11 is areturn spring 20, and a pressure receiving surface 19a, which is anupper surface of the piston 19, faces a compressed air supply port 12nformed in the upper section of the actuator cover portion 12. It shouldbe noted that a circular groove 19b is formed in a peripheral section ofthe piston 19, and an O-ring 21 and a backup ring 22 are fitted in thecircular groove 19b the former placed on the latter.

As described above, in the configuration of the present embodiment, afilm center of the diaphragm 7, central axes of the lower step 9 andupper step 13, a center of the aligning ball 16, a rotational center ofthe cam pinion 17, a central portion of the pressure receiving surface19a of the piston 19 are provided in a series along the axial directionof the housing 10.

FIG. 2 show s detailed configuration of the actuator housing portion 11,and spring guide pole 11d is formed at a position facing the rack guide11c with a pair of lacked round holes 11d₁, 11d₂ presented therein forthe return spring 20 to be mounted.

Also a pair of bearing blocks 11e, 11f are formed facing each other inboth sides of the rack guide 11c, and bearing holes 11g, 11h are formedin the two block 11e, 11f respectively. Herein the cam pinion 17 isprovided between the two blocks 11e, 11f, and the cam pinion 17 is bornby the rotating shaft 18 penetrated through the bearing holes 11g, 11h.

It should be noted that a male screw portion 11A screwed into a femalescrew portion of the actuator cover portion 12 is formed in a lowersection of the basic body of the actuator housing portion 11, and a malescrew portion 11B screwed into a female screw portion of the valvechamber 6 in the valve body 1 is formed in the small diameter section11a below it.

FIG. 3 shows a more detailed form of the cam pinion 17, and the camsurface portion 17A comprises a first cam surface portion 17A_(c) formedin a range of an rotating angle C so as to response to a case ofalways-closed type and a second cam surface portion 17A_(o) formed at asubstantially symmetrical position against a center O thereof in a rangeof the rotating angle O so as to respond to a case of always-open type,and the pinion portion 17B has 5 sheets of abutting teeth 17Ba formedalong circles provided at a specified pitch. Herein formed in the campinion 17 is a bearing hole 17b for the rotating shaft 18 to be insertedtherethrough as shown in FIG. 4, and also formed on the characteristicssurface 17Aa of the cam surface portion 17A is a arc surface along aspherical surface of the aligning ball 16. With this configuration, thecontacting state between the aligning ball 16 and the camcharacteristics surface 17Aa is stabilized.

It should be noted that FIG. 1 shows a mode of mounting the cam pinion17 when used as an always-closed type, but when used as an always-closedtype, the cam pinion is mounted, as shown in FIG. 3, in a state where itis rotated by 180 degrees around a horizontal line passing through thecenter O of the bearing hole 17b.

As shown in FIG. 3, the first cam surface portion 17A_(c) includes afirst cam characteristics surface portion 17A_(c1) and a second camcharacteristic surface portion 17A_(c2) communicated thereto, while thesecond cam surface portion 17A_(o) includes a first cam characteristicssurface portion 17A_(o1) and a second cam characteristics surfaceportion 17A_(o2) communicated thereto.

FIG. 5 is a diagram illustrating cam displacement of the cam surfaceportion 17A, namely a relation between the rotational angles C, O and atravel (distances L_(cs), L_(os) from the center O to the camcharacteristics surface as shown in FIG. 3). In the figure, thecharacteristic line L_(c) corresponds to the first cam surface portion17A_(c), while the characteristic line L_(o) corresponds to the secondcam surface portion 17A_(o).

A line segment (H-E) in the characteristic line L_(c) corresponds to thefirst cam characteristic surface portion A17_(c1) and a line segment(E-G) corresponds to the second cam characteristic surface portion17A_(c2), while a line segment (F-E) in the characteristic line L_(o)corresponds to the second cam characteristic surface portion 17A_(o2)and a line segment (E-I) corresponds to the first cam characteristicsurface portion 17A_(o1).

Herein the line segments (E-G), (F-E) correspond to a mode when a largeload is required in the entire pulsation range of the diaphragm 7 incases of the always-closed type and always-open type respectively, inother words to a mode when the vale is almost completely or completelyclosed, but either line segment is a straight line having a certainslope, so that, if a driving force of the piston 19 generated by apressure compressed air, namely a force generated by rotation of the campinion 17 is kept at a constant level, a constant load is applied to thediaphragm 17 regardless of the rotational angles C, O of the cam pinion17. In other words, a power amplifying ratio by a power amplifyingmechanism comprising the cam pinion 17 or others when the drivingmechanism comprising the piston 18 or others can be kept at a constantlevel.

A line segment (H-E) in the characteristic line L_(c) and a line segment(E-I) in the characteristic line L_(o) correspond to a mode when a smallload is required for the diaphragm 7 in cases of the always-closed typeand always-open type respectively, namely in a mode when an operationfor closing the valve is started. In the present embodiment, althoughthe slope is slightly larger than that when a large load is required asdescribed above, the line segments are set to a straight line having acertain slope respectively, and like in the case where a large load isrequired, if a force generated by rotation of the cam pinion 17 is keptat a constant level, a constant load is applied to the diaphragm 7. Itshould be noted that the second cam characteristic surface portions17A_(c2), 17A_(o2) may be formed so that a rotational angle and a poweramplifying ratio of the cam surface portion 17 satisfy a prespecifiedsubordinate relation, and also so that a change in a rotational angle ofthe cam pinion 17 and a load to the diaphragm 7 satisfy anon-subordinate relation. The configuration as described above isallowable because a loaded weight may be small when an operation forclosing the valve is started before the diaphragm contacts a valve headsection of the seal portion 5.

Next description is made for an example of operation in the presentembodiment constructed as described above.

FIG. 1 shows a state where the valve hole 4 has fully been opened,namely when no load is applied to the diaphragm 7. In this state, when apressure of compressed air supplied to a pressure receiving surface ofthe piston 19 is reduced to a prespecified level, the piston 19 goes updue to the energizing force of the return spring 20, and also the rackportion 19A integrally formed with the piston 19 moves upward.

With this operation, abutting and rotation of the pinion portion 17B ofthe cam pinion 17 is started, and the upper stem 13 and the lower stem 9start moving downward. And, when the cam pinion 17 has rotated by arange of the first cam characteristics surface portion 17A_(o1), thediaphragm 7 contacts a valve head section of the seal portion 5, andsubsequently (after passing the point E shown in FIG. 5) the upper step13 and lower step 9 move downward, following movement of the second camcharacteristic surface portion 17A_(o2) and applying a constant load tothe diaphragm 7. And when the cam pinion has rotated by a prespecifiedrotational angle C, for instance, by 60 degrees, the valve hole 4 iscompletely closed by the diaphragm 7.

In this case, as the cam surface portion 17 contacts the upper stem 13via the aligning ball 16, so that aligning between the cam surfaceportion 17A and the upper stem 13 or other component can smoothly beexecuted by making use of rotation of the ball 16.

FIG. 6 shows relations between a rotational angle of the cam surfaceportion 17 of the cam pinion and a power amplifying ratio in the presentembodiment as well as in a case where the conventional type of eccentriccam is used. As understood from this figure, the present embodiment, thepower in amplifying ratio is kept at a substantially constant value whenthe valve has almost completely or completely been opened, and the valuebecomes larger but is kept at a substantially constant level when thevalve has almost completely or completely been closed. Namely thisconfiguration provides the pulsation characteristics suited to thediaphragm that a load is kept at a small value when an operation forclosing the valve is started and is kept at a large value when the valvehas almost completely been closed.

In contrast, in the configuration using the conventional type ofeccentric cam, the power amplifying ratio monotonously decreasesaccording to a change of rotational angle, and in addition the load iskept at a maximum level when an operation for closing the valve isstarted, while the load is kept at a minimum level when the valve hasalmost completely been closed.

The present configuration corresponds to the always-closed type, and asan excessive load is applied during normal operation, 2 pieces of thereturn spring 20 are provided, and when corresponding to the always-opentype, the load relation becomes contrary to that in the normal state ofthe diaphragm 7. Namely no load is applied in the normal state, so thatonly one piece of return spring 20 is required.

Embodiment 2

FIG. 7 shows another embodiment of the present invention.

The embodiment shown in FIG. 7 is a variation of the configuration shownin FIG. 1, from which the ball 16, stem 13, and O-ring 14 have beenremoved.

Also the following improvements have been added thereto.

The surface of the cam pinion contacted by the ball in the cam pinion 17was changed to a flat one. The actuator housing 11 (valve body screwsection) was divided to two portions; an actuator housing and a bonnetwith a bush hole for guiding a lower section of the rack added anew andalso with the rack guide portion 11c removed therefrom. Also guides areadded to above the rack piston 19 and under the rack. In addition aguide bush hole was added to upper section of the actuator cover 12.

Parts added in FIG. 7 are as follows.

Rack piston guides 101a, 101b added to above the piston and under therack, bushes 100 for rack piston guides 101a, 101b, two pieces ofneedle-shaped roller 102 set in the right and left sides of the bearinghole 106 in the actuator housing, a needle-shaped roller with externalwheels 103, a bonnet 104, a stem 105 on which the roller with externalwheels 103 can be mounted, a stop screw 107 for setting the bonnet andthe actuator housing.

With the present embodiments, the following effects can be achieved.

By providing the wrapping guide 101a above the rack piston 19 and alsoproviding a wrapping guide 101b under the rack, operation of the rackpiston can be stabilized.

By using the needle-shaped roller 102 and the needle-shaped roller withexternal wheels 103, it becomes possible to minimize the frictionalresistance during operation.

By dividing the actuator housing 11 into the actuator housing 108 andbonnet 104 and fixing the two with the screw 107, it becomes possible toset lift when the valve is assembled.

By press fitting the bushes for guide 100, 106 into holes into which thewrapping guides 101a and 101b are inserted, resistance during operationof the rack piston is reduced.

Namely by providing guides above and under the rack piston 19 andsetting needle-shaped rollers on the cam pinion 17 and stem 105,transfer loss is reduced, and output can be increased.

INDUSTRIAL APPLICABILITY

With the invention of claim 1, a space for providing in the cylindricalhousing is effectively utilized as much as possible as compared to theconventional type thereof, which makes it possible to realize itsminimization. More particularly, a piston and a return spring eachconstituting a driving mechanism and a cam pinion and a rack portioneach constituting a power amplifying mechanism can efficiently beaccommodated in one cylindrical housing. Also as the cylindrical housinghas a simple cylindrical shape as a whole, the whole external shape isenhanced, the convenience in handling is improved, and in a case where,for instance, a plurality of shut-off valves are provided side by side,a length in a direction of their alignment can largely be reduced, andsimultaneously unnecessary physical interference arisen betweenadjoining shut-off valves can be avoided, and efficiency of working ondesigning of a piping system or installation thereof can be improvedthereby.

More particularly, in a cam pinion, a cam surface portion has beendesigned to be integrated into a pinion portion, while a piston has beendesigned to be integrated into a rack portion, which can contribute toreduction of a number of parts thereof, and also contribute to reductionof a number of processes for assembling.

With the invention of claim 2, configuration of the housing portion isas simple as the fact that an actuator cover portion is attached to theactuator housing portion, so that assembly of the housing is simple, andalso a cylindrical shape as a whole can easily be realized.

Also with the invention of claim 3, a diaphragm, a stem, a cam pinion,and a piston or the like are provided in a series in the axial directionof the cylinder, so that a longitudinal shape thereof as a whole cancontribute to simplification of its shape. Further the direction ofsupplying compressed air to a pressure receiving surface of the pistonbecomes substantially vertical to the pressure receiving surface of thepiston, so that driving efficiency can be improved. Furthermore arotational center of the cam pinion can coincide with a rotationalcenter of the cam surface portion, a diagram of the cam displacement caneasily be designed.

With the invention of claim 4, a range from a power amplifying mechanismof the cam pinion or the like to a portion of a driving mechanism a rackportion or the like is accommodated in a space for accommodation in theactuator housing portion, attachment thereto of the actuator coverportion can be easier.

With the invention of claim 5, a cam pinion and a stem can adequately bealigned, stable pulsation of a diaphragm can be expected.

With the invention of claim 6, a cam surface portion and a pinionportion can efficiently be used.

With the invention of claim 7, design of a cam displacement line is easyand a position of a stem is dominated by the position of the bearing ofcam pinion, so that it is not necessary to provide an adjustingmechanism for a position of the stem.

With the inventions of claim 8 and claim 9, assuming that a drivingforce of a driving mechanism is at constant level, a desired specifiedload can be added to the diaphragm when in a state of maximum loadaround a timing when the valve is completely closed, on the other hand,pulsating displacement of the diaphragm can be executed in any of theloaded state when in a state of minimum load around a timing when thevalve is completely opened, which becomes sufficiently appropriate topulsating characteristics of the diaphragm. Subsequently, the dispersionof reciprocal movement characteristics of a high pressure shut-off valvecan be omitted.

With the invention of claim 10, by only operation of changing a locationof one of cam pinions, the cam portion can be corresponded to analways-closed type or an always-open type thereof.

With the invention of claim 11, a number of attachments of the returnsprings can be selected according to its specification, moreparticularly in a case where an always-open type is selected, a numberof parts thereof can be reduced, which is convenient.

We claim:
 1. A diaphragm type high pressure shut-off valve having adiaphragm for opening and closing a valve port that is in flowcommunication with gas piping means for controlling a changing pressureof a gas flow within said gas piping means, and comprising a cylindricalhousing having a supply unit for receiving compressed air at one endthereof in an axial direction, a piston provided in the housing andadapted to reciprocate in response to a change in pressure of saidcompressed air, a return spring provided in the housing so as toenergize said piston against the change in pressure of said compressedair, a rack portion provided integrally with and extending from saidpiston and also having abutting teeth provided along the direction ofthe reciprocal movement of said piston, and a cam pinion having a pinionportion cooperatively engaging said rack portion teeth and also a camsurface portion integrally provided thereon and spaced from said pinionportion and also having a rotating shaft borne by said housing andextending in a direction crossing said axial direction of said cylinderat right angles, wherein rotational displacement of said cam surfaceportion of said pinion causes the cooperative engagement between therack portion teeth and said pinion portion by the reciprocating movementof said piston, while simultaneously said cam surface portioncooperatively engages a stem connected to the diaphragm to apply varyingforce to variably control the opening and closing of said shut-offvalve.
 2. A diaphragm type high pressure shut-off valve according toclaim 1, wherein said housing comprises an actuator housing portionhaving a space for accommodation at a substantially central portionthereof, and a substantially bottom-less cylindrical actuator coverportion attached to said actuator housing portion for covering thelatter.
 3. A diaphragm type high pressure shut-off valve according toclaim 1, wherein said supply unit for said compressed air including acentral portion of a surface of said piston for receiving a pressure ofsaid compressed air, a center of a rotating shaft of said cam pinion, ashaft core of said stem, and a central portion of a pulsing surface ofsaid diaphragm are located in a series in said axial direction of saidcylinder.
 4. A diaphragm type high pressure shut-off value according toclaim 2, wherein said cam pinion and stem are provided in a series insaid space for accommodation in said actuator housing portion and alsosaid return spring and said rack portion are accommodated therein.
 5. Adiaphragm type high pressure shut-off valve according to any of claims 1through 4, wherein said cam pinion has said cam surface portioncontacted through an aligning ball to said stem.
 6. A diaphragm typehigh pressure shut-off valve according to any of claims 1 through 5,wherein said cam pinion is generally disk-formed, said pinion ispresented in the substantially semi-circular portion, and a cam surfaceportion is formed in another substantially semi-circular portion.
 7. Adiaphragm type high pressure shut-off valve according to any of claims 1through 6, wherein said cam surface portion has the cam displacementcharacteristics that the travelling distance varies according to acenter of a rotating shaft of said cam pinion.
 8. A diaphragm type highpressure shut-off valve according to claim 1, wherein said cam surfaceportion has a first cam characteristics surface portion formed so that apower amplifying ratio which is a ratio of said pressurizing forceversus a load to the diaphragm is kept at a substantially constant levelagainst a change in the rotating angle, and a second cam characteristicssurface portion.
 9. A diaphragm type high pressure shut-off valveaccording to claim 8, wherein said first cam characteristic surfaceportion corresponds to a portion having a larger pulsation rate in anentire pulsating portion of said diaphragm, and said second camcharacteristics surface portion corresponds to a remaining portionhaving a smaller pulsation rate.
 10. A diaphragm type high pressureshut-off valve according to claim 8 or claim 9, wherein said cam surfaceportion is formed so that it encloses a first cam surface portioncorresponding to an always-closed type in which said valve hole isclosed when a pressure by said compressed air is reduced and a secondcam surface portion corresponding to an always-open type in which saidvalve hole is opened when a pressure by said compressed air is reduced.11. A diaphragm type high pressure shut-off valve according to claim 10,wherein said return spring comprises a coil spring in which saidenergizing force can selectively be set.
 12. A diaphragm type highpressure shut-off valve according to claim 8, wherein said second camcharacteristics surface portion is formed so that said power increaseratio is dependent in a prespecified relation on a change in therotating angle.
 13. A diaphragm type high pressure shut-off valveaccording to claim 8, wherein said second cam characteristics surfaceportion is formed so that said power increase ratio is independent of achange in rotating angle.